James Buchanan is most often remembered as the President who effectively allowed the southern states to form a Confederacy and leave the Union, setting the stage for a massive Civil War which would be waged and won by Abraham Lincoln, his successor. Few people today realize how close the country came to having the crisis of the firing on Fort Sumter handled by Vice President John C. Breckinridge instead of by Buchanan. Had the attempted assassination of Buchanan been a success, Breckinridge would have assumed the Presidency in 1859. A whole different set of decisions might have averted or delayed the Civil War.
By the end of the Utah War in 1858, Buchanan was universally despised among Mormons. What amounted to a series of misunderstandings led to the movement of about a third of the US army into Utah. There were few casualties during the war, but enormous loss of property occurred. Many Mormons were forced to abandon their farms and crops as Buchanan's army approached. One of those evacuees was Jacob Christofferson, whose wife became ill and died during their journey to central Utah. Even after peace was made, Christofferson held a deep grudge against the man whom everyone eventually agreed was responsible for the war.
On November 12th, 1859 President Buchanan walked between the White House and the Capitol building (the Secret Service was not created until 1865). Christoffersen approached him, attracting the attention of an aide. The man drew a Philadelphia deringer (similar to that later used by John Wilkes Booth to assinate Lincoln) and fired towards Buchanan's chest. Buchanan collapsed to the ground as Christoffersen ran away.
Little did Christoffersen guess that Buchanan was completely unharmed. Buchanan later said that he was "... quite startled at the report of the pistol and at the sensation of a blow to my chest," causing him to fall over. But the bullet failed to penetrate Buchanan's clothing and was found on the ground in perfect condition.
It is commonly thought that Christoffersen accidentally 'short-started' the bullet, failing to fully seat the wadding in front of the muzzle-loaded weapon. The ball would have rolled forward by a few millimeters, causing a gap between powder and ball that prevented the projectile from being propelled to proper velocity. This problem was common in handguns of the era, which might have been perfectly functional when first loaded but later jostled loose after being carried in a pocket for some time.
Christoffersen was found to have hanged himself in his room at a cheap boarding house that night. His face was identified by the aide who had accompanied Buchanan. It is not known whether the would-be assassin died believing that he had succeeded in killing the President.